Motor-starter.



G. D. KNIGHT.

MOTOR STARTER; APPLICATION FILED NOV. 12, 1908.

' PatentedOct. 14, 1913.

INSZE'NTUR CHARLES 17. KNIEHT.

WI TJYEE'SES" ductioirmotors of the UNITED STATES PATENT QFFICE.

'UHABLES D. KNIGHT, OE SCHENEGTADY, NEW YORK, ASSIGNOB, T GENERALELECTRIC COMPANY,

A CORPORATION OF NEW YORK.

MOTOR-STABTER.

Specification of Letters Patent.

Patented Oct. 14,1913.

Application filed November 12, 1908. Serial No. 462,218.

To all whom it may concern Be it known that I, CHARLES D. KNIGHT, acitizen of the United States, residing at Schenectady, county ofSchenectady, State of New York, have invented certain new and usefulImprovements in Motor Starters, of which the following is aspecification.

This invention relates to means for controlling electric motor circuitsand has for its object the provision of a device whereby an electricmotor may be started and brought to. running speed in a safe andciticient manner.

My invention relates more specificallyto the starting of alternatingcurrent motors of the induction type. When starting inslip ring type, itis essential that the secondary circuit be closed through the necessaryresistance before the closing of the primary circuit. It is desirablethat means he provided for cutting the impedance out of the secondarycircuit in a convenient manner. In carrying out my invention, therefore,I provide in connection with automatic means for cutting the resistanceout of the secondary circuit, means'whereby the resistance may beautomatically reinserted in the secondary circuit upon the opening ofthe rimary circuit. also provide means whereiiy the primary circuitcannot be closed until said resistance is inserted in the secondarycircuit.

In the accompanying drawing I have shown my invention embodied inconcrete form, the arrangement being somewhat diagrammatic in order tomake the operation of my device more apparent.

Referring to the drawing, P represents the primary and S the secondaryof an inv duction motor, of the slip ring type. I have shown a motorhaving three phase windings, although it is apparent that my inventionis not limited to any particular number of phases. The primary circuitof the motor is closed by means of contactors A, B and C, one for eachphase, having solenoids a, Z) and 0 respectively, actuating plungers,which plungers operate contacts to open the primary circuit at contacts1, 2 and 3 respec tively. The plungers of solenoids a and c carrybridging contacts i and 5 respectively, arranged to bridge contacts 6and 7 as shown, for a purpose hereinafter described. The impedance forthe secondary circuit which I have shown as a resistance is diarrangedto bridge the vided into three sections, D, E and F, one for each phase.These resistances are provided with contact studs 8, 9 and 10 arrangedin a circle, the sections being separated by dead studs. The controllingmemher for this resistance consists of three arms 11, 12 and 13, joinedtogether by an operating disk 14: and arranged 120 apart. On each arm isarranged a bridging contact 15 contacts 16 successively and shortcircuit resistance 16 normally in series with coils a, b and 0. Thecontrolling member is arranged so that it is always operated in the samedirection, namely, a clockwise direction by means of a pawl 17 pivotedon an arm 18. This arm 18 is pivoted on the pivotal point of the controlling member at 19, while its free endis actuated by means of thesolenoid 20 in one direction and returned by the spring 21. The returnmovement of the solenoid is retarded by the dash pot 22. The make andbreak mechanism of the step by step sole noid operating mechanismconsists of two pivoted arms 23, one of which is arranged to vibratebetween the studs 24: and 25 while the other arm is engaged by the stops26 and 27 on the plunger of the solenoid.

The spring 28 draws the two arms toward each other: It is evident thatthe arm 23 will be moved into engagement with either stud 2a or 25depending upon which side of the pivotal point the spring28 happens tobe. It isalso apparent that as soon as the two points of support of thespring and the pivotal point of the rods pass out of line with eachother, that the switch 23 will be snapped over witha quick movement.This type of mechanism' is well known and requires no furtherdescription. The limit switch 29 is arranged to be 'en gaged by each armin turn as it arrives at the end of the adjacent section of theresistance.

anism. A shunt is arranged around this switch from the point 30 throughconductor 31, contacts i and 5 to point 32, so that when the bridgingcontacts l-and 5'are in engagement with the contacts 6 and 7respectively. the switch will be short circuited and the circuit of thesolenoid operating mechanism closed.

The arrangement of circuits and mode of operation is as follows:

This switch opens the circuitbf the solenoid 20 and stops the operatingmech- When the switch 1 33 is closed, the parts being in'the positionshown, current will pass under phase X, through coils, a, Z) and c inparallel, thence through conductor 84, contacts 16 and conductor 35backto phase Y. The circuit of the primary P is thus closed throughcontacts 1, 2 and 316mm the three phases X, Y and Z. At the same timecurrent passes from phase X, through conductor 36, solenoid 20,, contact25, switch 29 and conductor 35 back to phase Y. The solenoid 20 beingenergized, the arm 18 is moved to the left and the controlling arms 11,12 and 13 stepped along to the next stud. When the circuit of thesolenoid is broken at 25, the arm 23 of the vibrator snaps over to stud24 and spring 21 returns the plunger which is re-' tarded by the dashpot22. This movement continues in a well known manner, stepping the armsover the studs until the arm 11 reaches the limit switch 29 and opensthe circuit of the solenoid 20. At this point, the resistance is cut outof the secondary circuit, and the motor is running at normal speed. If,now, the voltage should fail, the contactors A, B and C would open. Whenthis happens the contacts 6 and 7 will be bridged and the circuit ofthesolenoid 20 will be immediately closed through conductor 31, bridgingcontacts 4 and 5, and conductor 35, instead of through the limit switch.Upon restoration of voltage to the line the control arms will be movedforward, each arm moving on to the first step of the succeeding sectionof resistance. The resistance is thus all included in the secondarycircuit so that upon the closing of the primary circuit the motor willbe protected.

It is evident that when the primary circuit is opened, it cannot againclose until the arms are brought'to the starting position to bridgecontacts 16 and short circuit re sistance 16". This is so because theresistance 16 is of such a value that when it is in series withsolenoids (1,6 and c, the latter will hold their contactors closed, butwill I not be strong enough to close the contactors.

It will be seen that I have provided a very simple and efiicientstarting device which adequately protects the motor against damage dueto careless handling and the like. The motor will start andautomatically come up to running speed and when the motor stops leavethe apparatus in protected position.

While I have described my invention in connection with concretemechanism for bringing about the desired result, it should be understoodthat I do not limit my invention thereby, sincevssious modificationswill suggest themselves i6" those skilled in the art without departingfrom the spirit of my invention, the scope of which is set forth in theannexed claims.

WVhat I claim as new and desire to secure by Letters Patent of theUnited States, is 1. The combination with an alternating current motor,of means for controlling the same comprising a primary circuit closingdevice, an impedance for the secondary circuit, an electro-magneticdevice for gradually reducing said impedance by a movement in onedirection and connections established upon the failure of voltagewhereby the device is automatically moved in the same direction toinsert impedance upon the restoration of voltage.

2'. T he combination with a polyphase motor, of means for controllingthe same comprising a primary circuit closing device, an impedance foreach phase of the secondary circuit, a controlling member having avarying element for each impedance, an electromagnetic device for movingsaid member in a direction to reduce the impedance, 2. switch forstopping said member at the limit of its movement, and connefitionsestablished upon the failure of voltage whereby the member is movedinthe same direction to insert the impedance upon the restoration ofvoltage 3. The combination with a olyphase motor, of means forcontrolling t e same, comprising a primary circuit closing device, animpedance for the secondary circuit having concentrically arrangedsections, one for each phase, a controlling member having an arm foreach section, an electromagnetic mechanism for moving said member in adirection to reduce the impedance, means for stopping said member whenit reaches the end of a section, and connections established upon theopening of the primary circuit by failure of voltage whereby saidmechanism is energized to continue the movement of each arm to the nextsection upon the re storation of voltage.

l. The combination with a polyphase m0- tor, of means for controllingthe same comprising a primary circuit closing device, an impedance forthe secondary circuit having concentrically arranged sections one foreach phase, a controlling member having an arm for each section, anelectromagnetic device for moving said member in a direction to reducethe impedance, a switch for stopping said member when it reaches the endof a section and a shunt around said switch arranged to be closed uponthe opening of the primary circuit by failure ofvoltage to continue themovement of each arm to the next section upon the restoration ofvoltage.

5. The combination with a polyphase motor, of means for controlling thesame comprising a primary circuit closing device, an impedance for thesecondary circuit having concentrically arranged sections one for eachphase, a controlling member having an arm for each section, anelectromagnetic device for moving said member in a direction to reducethe impedance, a switch forstopping said member when it reaches the endof a section, a shunt around said switch arranged to be closed upon theopenin of the primary circuit by failure of v0 tag'e to continue themovement of each arm to the next section upon the restoration of voltageand connections whereby the primary circuit cannot be closed until thecontrolling arms are at the beginning of a section;

6. The combination with a polyphase motor, of means for controlling thesame comprising a primary circuit closing device, an impedance for thesecondary circuit having concentrically arranged sections one for eachphase, a member having an arm for each section, an electromagnetic stepby-step decopies of this patent may be obtained for in cents each, 'byaddressing the Commissioner of vice arranged vto always more said memberance, a switch for stopping said member when it reaches the end of thesection and a closed upon the o ening of the rimary circuit by failure 0voltage to continue the movement of each arm to fthe beginning of thenext section upon the restoration of voltage.

myhand this 10th day of November, 1908.

" CHARLES D. KNIGHT.

Witnesses: I v

BENJAMIN B. HULL, HELEN ORFORD.

taunts:

Wuhington, D. 0..

shunt around said switch arranged to be In witness whereof, I havehereunto set in the same direction to reduce the imped-

